Rotor blade construction for circulation control aircraft

Abstract

A circulation control aircraft rotor blade having a spanwise Coanda surface 16 and a plurality of spanwise extending flexible composite material panels 18 cooperating with the surface to define slots for the discharge of compressed air from within the blade with each panel having first flexure means 60 associated with screw adjustments 36 for establishing a slot opening preload and second flexure means 62 associated with screw adjustments 38 for establishing a slot maximum opening.

We claim: 
     
       1. A rotor blade for a circulation control aircraft having along a portion of its span an edge section consisting of a Coanda surface, a duct located within said edge section for providing compressed air to be discharged adjacent the top of the Coanda surface to flow around the outside of the Coanda surface, and flexible panel means for controlling compressed air discharge, said panel having a first edge fixedly connected to the upper outside surface of said edge section and a second edge defining with an upper portion of the Coanda surface a spanwise extending slot through which compressed air is discharged, said panel also having first flexure means associated with first means for establishing a preload on said panel second edge so that said slot is closed until a minium duct air pressure is reached, and second flexure means associated with second means for limiting the movement of said panel second edge in response to duct air pressure so as to establish a maximum slot opening, said first flexure means including a composite panel length area of specific thickness and layup to provide desired flexing characteristics and said second flexure means including a composite panel length area of different specific thickness and layup to provide different flexing characteristics than said first flexure means. 
     
     
       2. A rotor blade for a circulation control aircraft having along a portion of its span an edge section consisting of a Coanda surface, a duct located within said edge section for providing compressed air to be discharged adjacent the top of the Coanda surface to flow around the outside of the Coanda surface, and flexible panel means for controlling compressed air discharge, said panel having a first spanwise edge portion fixedly connected to the upper outside surface of said blade edge section, a second spanwise edge portion defining with an upper portion of the Coanda surface a spanwise extending slot through which compressed air may be discharged, and a mid-spanwise portion between said panel first and second spanwise edges, first adjustment means associated with said mid-spanwise portion for establishing a preload on said panel second spanwise edge portion so that said slot may be closed until a minimum duct air pressure is reached and second adjustment means associated with said second spanwise edge portion for establishing a maximum slot opening, the elastic properties of the panel between said fixedly connected edge portion and said mid-spanwise portion being different than the elastic properties of the panel between said mid-spanwise portion and said second spanwise edge portion.